Coating device for producing a thin layer of a fluid or semi-fluid material

ABSTRACT

To coat the upper surface of a file of plates laid in end-to-end relation, a box frame containing the material to be applied and having an open bottom is moved longitudinally of the file of plates. The thickness of the coating is determined by vertical adjustment of the lower edge of a trailing and transversely extending control bar on the frame above the upper surface of the plates, the frame also being provided with a leading transversely extending control bar which engages the upper surface of the plates and lateral guide walls engageable with the sides of the plates for longitudinal guidance of the frame. Sealing strips located at the inside surface of the laterally positioned guide walls function to maintain a uniform thickness of the applied coating regardless of variations in plate thickness.

United States Patent Nybom, deceased [s41 COATING DEVICE FOR PRODUCING A THIN LAYER OF A FLUID 0R sEMI- FLUID MATERIAL [72] Inventor: Nib Goran Nybom, deeeaed, late of Kristianstad, Sweden by Ethel Barbro Louise Nybom, administratrix [73] Assignee: AB Instruments, Lund, Sweden [22] Filed: Feb. 11, 1971 [21] Appl. No.: 114,643

[451 July 18,1972

FORFJGN PATENTS OR APPLICATIONS 448,551 3/1949 Italy ..1 18/415 Primary Examiner-Henry S. Jaudon Attorney-Pierce, Schetfler 8: Parker ABSTRACT To coat the upper surface of a file of plates laid in end-to-end relation, a box frame containing the material to be applied and having an open bottom is moved longitudinally of the file of plates. The thickness of the coating is determined by vertical adjustment of the lower edge of a trailing and transversely extending control bar on the frame above the upper surface of the plates, the frame also being provided with a leading transversely extending control bar which engages the upper surface of the plates and lateral guide walls engageable with the sides of the plates for longitudinal guidance of the frame. Sealing strips located at the inside surface of the laterally positioned guide walls function to maintain a uniform thickness of the applied coating regardless of variations in plate thickness.

6Clalms,9DrawlngFlgures Patented Jul 18, 1972 3,677,227

3 Sheets-Sheet 1 Patented July 18, 1972 3,677,227

3 Sheets-Sheet :3

Patented July 18, 1972 3 Sheets-Sheet 5 COATING DEVICE FOR PRODUCING A THIN LAYER OF A FLUID OR SEMI-FLUID MATHIIAL The present invention relates to a device for coating a thin layer of a fluid or semifluid material, for instance a powder suspension, on a fiie of plates of substantially the same width and thickness and preferably also of substantially the same length. Alternatively, the length of the plates may be equal to different multiples of the same unit of length in that, for instance, some plates may be twice as long as other plates in the same file. The device consists of a frame comprising the following main components: (a) a front guide wall or guide bar adapted to be adjusted normally to the longitudinal direction of the plates and then to be moved in said direction contacting the plates, (b) a rear control wall or control bar defining the thickness of the layer and adapted to travel without contacting the plates so as to form a space between itself and the plates, and (c) lateral guide walls or lateral guide bars extending in parallel with each other and with the longitudinal direction of the file of plates, the distance between said lateral walls being larger than the width of the plates. Said lateral walls reach below the top surfaces of the plates in order to be guided by the lateral edges thereof.

The device according to the invention is characterized in that the frame inside each of said lateral guide walls is provided with sealing strips disposed in such a raised position relatively to said front guide bar and said rear control bar that they do not touch the plates when the thickness of the plates have normal variations.

The device according to the invention is particularly well adapted for spreading the adsorption layer on plates designed for thin layer chromatography. Said layer preferably is produced by means of a suspension of, for instance, silica gel, polyamide powder or cellulose powder. The device, however, of course also may be used on other occasions where it is desired to produce a thin uniform coating layer on a number of substantially similar plates of glass or another material.

The advantages of the invention will best appear from the following specification wherein the invention is described with reference to the accompanying drawings which by way of example illustrate a preferred embodiment of the invention.

FIG. I is an exploded view of the elements forming parts of the device.

FIG. 2 is a top plan view of the assembled device.

FIG. 3 is a side elevation view of the device.

FIG. 4 is a rear elevational view of the device.

FIG. 5 is a front elevation view of the device.

FIGS. 6, 7 and 8 are schematic longitudinal sectional views illustrating the course of events when moving the device from one plate onto another one when certain conditions to are fulfilled (FIGS. 6 and 7) and when said conditions are not fulfilled (FIG. 8).

FIG. 9 illustrates the sliding movement of the spreading device along a long file of plates.

As most clearly appears from FIG. I, the device comprises a front guide bar 1, a rear control bar 2, two lateral guide bars 3, two sealing strips 4, a front edge strip 5, a rear edge strip 6, a stiffening bar 7 and two spacers 8. Elements 1-7 may be fixedly secured together by conventional means.

As most clearly appears from FIG. 2, the spacers may be adjustably secured in desired positions by bolts 9 and 10. Preferably, the spacers 8 are vertically displaceable. This may be accomplished, for instance, by providing oval openings II in the spacers and/or oval openings 1 l in the lateral bars 3.

The use of the device most clearly appears from FIG. 9. A file of plates 12, for instance X 15 cm glas plates, is disposed on a table. The coating device is adjusted with the rear end edge thereof adjacent one of the ends of the file of plates. Then the coating device is filled with the powder suspension or the like to be applied alter which the device is moved along the file of plates with a uniform speed.

In order that the device should operate satisfactory it is important that the dimensions as shown in FIGS. 3, 6 and 7 fulfil certain conditions. Said dimensions and conditions, respectively, may be defined as follows:

c =the layer thickness which may be variable (FIGS. 6 and c the srmllest layer thickness which is contemplated.

d the variation of diflerent plates thicknesses (FIG. 7

p,,,,,,==the smallest plate thickness (FIGS. 6 and 7).

p, =the greatest plate thicknem (FIGS. 6 and 7).

a the spacing between the bottom of the sealing strip and the bottom of the front guide bar.

b the spacing between the bottom of the sealing strip and the bottom of the rear control bar.

e the spacing between the bottom of the lateral guide walls and the bottom of the front guide bar.

f the spacing between the bottom of the lateral guide walls and the bottom of the rear control bar.

b dc When the above-mentioned conditions are not fulfilled the phenomen shown in FIG. 8 easily arises, i.e., when the device is moved from the plate 124 onto the plate 12b it will rest with its sealing strips 4 on the edge 13. As long as said contact with the edge 13 exists the whole spreading device can uncontrollably rock about said edge and this will result in unwanted variations in the layer thickness.

When the above-mentioned conditions are fulfilled, however, there will always be a gap 14 between the edge 13 and the sealing strips 4, as is shown in FIG. 6. In this case there will only arise a jerk in the movement as the front guide bar 1 drops from the plate 12a onto the plate 12b. However, by selecting the length of the spreading device substantially equal to the length of the plate it is possible to control the movement so that said jerk always occurs when the gap 15 is adjacent one of the edges of a plate.

Similarly, it appears from FIG. 7 that when the above-mentioned conditions are fulfilled there will also be a gap 17 between the edge 16 and the sealing strips 4 when passing from a thinner plate 12: onto a thicker plate 1 2d.

In practice the production of plates for thin layer chromatography has shown that one may reckon on a nominal plate thickness of 1.7 mm and further that one may normally assume that the maximum variation of the plate thickness is about 0.5 mm d. (FIG. 7) Then the smallest plate thickness p may be calculated at 1.45 mm. When a minimum layer thickness of e 0.25 mm is desired, this condition results in that a should be larger than 0.5 mm, b larger than 0.25 mm, 2 smaller than 1.45 mm and f smaller than 1.7 mm. Thus, the dimensions a and b are important for the formation of uniform layers even when there is a certain variation of the plate thickness. The dimensions 2 and f are important in order to prevent the spreading device on a thin plate from resting on the table.

Naturally, the invention is not restricted to the embodiment described above only or to the dimensions stated there by way of example but is restricted only by the following claims. Thus, for instance, it is of course not necessary that the spreading device is composed by a great number of bars. Also, in larger devices it may be appropriate to produce them by means of injection moulding or by moulding them in one single element or in a fewer number of parts which afterwards are assembled.

It is claimed:

l. A device for producing a thin layer of a fluid-like material of a file or plates having substantially the same width and thickness comprising, a rectangular box frame having an open bottom, said frame including a front guide bar extending transversely of said box frame and adapted to contact said file of plates, a rear control bar extending transversely of said box frame, means for spacing said rear control bar above said file of plates to define the thicknes of the layer to be produced on said plates, parallel lateral guide walls extending longitudinally of said box frame, said guide walls being spaced apart a distance greater than the width of the file of plates and extending below the top surfaces of said file of plates so that said box frame will be guided by the lateral edges of said guide walls and a sealing strip disposed on each of the inside surfaces of said guide walls, the bottom edges of said sealing strips being raised above said from guide bar and said rear control bar so as to be spaced from the top surfaces of the file of plates when slight variations in thickness may occur.

2. A device as claimed in claim l wherein said spacing means for said rear control bar comprises two spacer elements disposed at the ends of said rear control bar, said spacer elements resting on the tile of plates.

3. A device as claimed in claim 2 wherein said spacer elements are adjustable for controlling the space between said rear control bar and the file of plates.

4. A device as claimed in claim 1 and further comprising a stiffening bar extending transversely of and at the approximate midpoint of said box frame and disposed at the upper portions of said lateral guide walls and parallel to said front guide bar and said rear control bar, said stiffening bar serving as a handie for manually moving said box frame along the file of plates.

5. A device as claimed in claim I wherein the length of said box frame is substantially equal to the length of each plate of the file.

6. A device as claimed in claim 1 wherein the from bottom edge of said front guide bar is rounded to facilitate movement over plates having slightly different thicknesses.

I I t t I 

1. A device for producing a thin layer of a fluid-like material of a file or plates having substantially the same width and thickness comprising, a rectangular box frame having an open bottom, said frame including a front guide bar extending transversely of said box frame and adapted to contact said file of plates, a rear control bar extending transversely of said box frame, means for spacing said rear control bar above said file of plates to define the thickness of the layer to be produced on said plates, parallel lateral guide walls extending longitudinally of said box frame, said guide walls being spaced apart a distance greater than the width of the file of plates and extending below the top surfaces of said file of plates so that said box frame will be guided by the lateral edges of said guide walls and a sealing strip disposed on each of the inside surfaces of said guide walls, the bottom edges of said sealing strips being raised above said front guide bar and said rear control bar so as to be spaced from the top surfaces of the file of plates when slight variations in thickness may occur.
 2. A device as claimed in claim 1 wherein said spacing means for said rear control bar comprises two spacer elements disposed at the ends of said rear control bar, said spacer elements resting on the file of plates.
 3. A device as claimed in claim 2 wherein said spacer elements are adjustable for controlling the space between said rear control bar and the file of plates.
 4. A device as claimed in claim 1 and further comprising a stiffening bar extending transversely of and at the approximate midpoint of said box frame and disposed at the upper portions of said lateral guide walls and parallel to said front guide bar and said rear control bar, said stiffening bar serving as a handle for manually moving said box frame along the file of plates.
 5. A device as claimed in claim 1 wherein the length of said box frame is substantially equal to the length of each plate of the file.
 6. A device as claimed in claim 1 wherein the front bottom edge of said front guide bar is rounded to facilitate movement over plates having slightly different thicknesses. 